Statistical Modelling and Mechanical Behaviour of Biochar-Reinforced Hybrid Composites: A Response Surface Approach

The present research investigates the mechanical properties (tensile, flexural & impact) of kenaf-flax-based hybrid composites with the incorporation of various weight percentages of coconut shell biochar. The hybrid composites were fabricated through compression molding with the following parameters: varying flax to kenaf ratios (0-100%), biochar content (2-6 wt.%), and fiber loading (20-40 wt.%) according to a Response Surface Methodology (RSM) and Box-Behnken Design (BBD). The ANOVA analysis of the composites confirmed that the quadratic models were statistically significant for high coefficients of determination, i.e., R²>98. Among the three variables, the flax-to-kenaf weight ratio and fiber loading were found to be the maximum leading variables, while the biochar also provides the best results up to 4 wt.%. The RSM method demonstrates the maximum mechanical properties (tensile 110 MPa, flexural 150 MPa, and impact 13 kJ/m²) were achieved at 60% of flax, 40% of kenaf, 35 wt.% of fiber loading, and 4 wt.% of biochar. The fracture analysis of the hybrid composites was evaluated through scanning electron microscopy (SEM). The obtained results of hybrid composites reveal that the inclusion of biochar content enhanced the performance of natural fiber composites, providing sustainable alternatives for structural applications.